一、linq高级查

1.模糊查（包含）

1  public List
     
       Select(string name)2     {3         return con.User.Where(r =>r.UserName.Contains(name)).ToList();4     }
     

2.查开头

public List
     
       Select(string name)    {        return con.User.Where(r => r.UserName.StartsWith(name)).ToList();    }
     

3.查结尾

public List
     
       Select(string name) {        return con.User.Where(r => r.UserName.EndsWith(name)).ToList();    }
     

4.个数

clist.Count()

5.最大值：Max(r => r.price);

public decimal? SelectMax()    {        return con.car.Max(r => r.price);    }

6.最小值：Min(r => r.price);

public decimal? SelectMin()    {        return con.car.Min(r => r.price);    }

7.平均值：Average(r => r.price);

public decimal? SelectAvg()    {        return con.car.Average(r => r.price);    }

8.求和：Sum(r => r.price);

 public decimal? SelectSum() { return con.car.Sum(r => r.price); } 

9.排序：

1、OrderBy 按升序对值进行排序。

2、OrderByDescending 按降序对值进行排序

3、ThenBy 按升序执行次要排序。

4、ThenByDescending 按降序执行次要排序。

（1）升序：OrderBy(r => r.price)

1   public List
     
       orderBy()2     {3         return con.car.OrderBy(r => r.price).ToList();4     }
     

（2）降序：OrderByDescending(r => r.price)

public List
     
       orderBy()    {              return con.car.OrderByDescending(r => r.oil).ToList();    }
     

二、分页与组合查询

1.分页

1 public List
     
       Select(int count, int number)2     {3         return con.User.Skip(count * (number - 1)).Take(count).ToList();4     }
     

public int MaxPageNumber()    {        List
     
       list = new UserData().Select();        double nu = list.Count / (Pagecount * 1.0);        int num = Convert.ToInt32(Math.Ceiling(nu));        return num;    }//总页数
     

void btn_next_Click(object sender, EventArgs e)    {        int NowNumber = Convert.ToInt32(Label2.Text) + 1;        if (NowNumber > MaxPageNumber())        {            return;        }        Repeater1.DataSource = new UserData().Select(Pagecount, NowNumber);        Repeater1.DataBind();        Label2.Text = NowNumber.ToString();        DropDownList2.SelectedValue = NowNumber.ToString();    }//下一页

2.组合查询

1 void Button2_Click(object sender, EventArgs e) 2     { 3     using(WebDataContext con=new WebDataContext()){ 4         var All = con.User.AsEnumerable(); 5         if (TextBox1.Text.Trim().Length > 0) 6         { 7             var namelist = con.User.Where(r => r.UserName.Contains(TextBox1.Text.Trim())); 8  9             All = All.Intersect(namelist);10         }11 12         if (tb_sex.Text.Trim() == "男" || tb_sex.Text.Trim() == "女")13         {14             var sexlist = con.User.Where(r =>Convert.ToBoolean(r.Sex)==(tb_sex.Text.Trim()=="男"?true:false));15 16             All = All.Intersect(sexlist);17         }18 19         if (tb_age.Text.Trim().Length > 0)20         {21              int nowyear = DateTime.Now.Year;22             try {23              int age=  Convert.ToInt32(tb_age.Text.Trim());24              int g = nowyear- age;25              DateTime d = Convert.ToDateTime(g.ToString() + "-1-1");26              if (DropDownList3.SelectedValue == ">=")27              {28                  var agelist = con.User.Where(r => Convert.ToDateTime(r.Birthday) >= d);29                  All = All.Intersect(agelist);30 31              }32              else33              {34                  DateTime dd = Convert.ToDateTime(g.ToString() + "-12-31");35                  var agelist = con.User.Where(r => Convert.ToDateTime(r.Birthday) <= dd);36                  All = All.Intersect(agelist);37 38              }39             }40             catch{41             }           42         }43 44 45         Repeater1.DataSource = All;46         Repeater1.DataBind();47     }48     }